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Annotation of researchv9/cmd/emacs/findtty.c, revision 1.1

1.1     ! root        1: #include <stdio.h>
        !             2: #include "stddefs.h"
        !             3: #include <sys/types.h>
        !             4: #include <sys/stat.h>
        !             5: #include <utmp.h>
        !             6: 
        !             7: /* Returns a pointer to a character string containing the tty name of a
        !             8:  * logged-on user.  If the user is logged on more than once, the tty
        !             9:  * returned is the one that has been used most recently.  If the user is
        !            10:  * not presently logged on, the null string is returned.  Each call to
        !            11:  * findtty returns a pointer to the same data area, so the string must
        !            12:  * be copied if it is to be used again.
        !            13:  *
        !            14:  * NOTE: if this code is compiled with the "-DMAIN" option, then a main
        !            15:  * program will be produced, instead of a function.  The main program
        !            16:  * takes one user name as argument and outputs the ttyname on standard
        !            17:  * output.
        !            18:  *
        !            19:  * J. Leth, IH 6E-318, x6133.
        !            20:  */
        !            21: 
        !            22: #define NAMELEN        8
        !            23:        /* Max. number of characters in a login name */
        !            24: #define TTYLEN 8
        !            25:        /* Max. number of characters in a tty name */
        !            26: 
        !            27: #ifndef MAIN
        !            28: char *
        !            29: findtty(user)
        !            30:        char *user;     /* user login name */
        !            31: {
        !            32: 
        !            33: #else
        !            34: main(argc, argv)
        !            35:        int argc;
        !            36:        char *argv[];
        !            37: {
        !            38:        char *user;
        !            39: #endif
        !            40: 
        !            41:        extern long ftime();
        !            42:        extern int strcmp();
        !            43: 
        !            44:        FILE *f;
        !            45:        struct utmp buf;
        !            46:        long ttytime = 0L;
        !            47:                /* Holds latest access time found for requested user */
        !            48:        static char ttyname[TTYLEN+1];
        !            49:                /* Holds name of tty with that access time */
        !            50:        long acc_time = 0L;
        !            51:                /* Access time of tty currently being considered */
        !            52:        char *utmp = "/etc/utmp";
        !            53: 
        !            54:        if((f=fopen(utmp,"r"))==NULL) {
        !            55:                errexit("findtty: can't open %s file.\n", utmp);
        !            56:        }
        !            57: 
        !            58:        ttyname[0] = NUL;
        !            59: 
        !            60: #ifdef MAIN
        !            61:        if (argc != 2) {
        !            62:                usage("Usage:\tfindtty <login-id>\n\
        !            63:        Outputs the name of the most recently-used terminal on which\n\
        !            64:        user <login-id> is currently logged in.\n");
        !            65:        }
        !            66: 
        !            67:        user = argv[1];
        !            68: #endif
        !            69: 
        !            70:        while(fread(&buf,sizeof(buf),1,f) == 1) {
        !            71:                /* Search utmp file for logins of the designated user.
        !            72:                 * For each one found, see if the access time is later
        !            73:                 * than the latest one so far; if it is, remember the
        !            74:                 * ttyname and ttytime.
        !            75:                 */
        !            76: 
        !            77:                if(strncmp(buf.ut_name, user, NAMELEN) != 0)    continue;
        !            78: 
        !            79:                if((acc_time=ftime(buf.ut_line)) > ttytime) {
        !            80:                        ttytime = acc_time;
        !            81:                        strncpy(ttyname, buf.ut_line, TTYLEN);
        !            82:                        ttyname[TTYLEN] = '\0';
        !            83:                                /* just to be sure string is terminated */
        !            84:                }
        !            85:        }
        !            86: #ifndef MAIN
        !            87:        return(ttyname);
        !            88: #else
        !            89:        printf("%s\n", ttyname);
        !            90: #endif
        !            91: }
        !            92: 
        !            93: long
        !            94: ftime(s)
        !            95: char *s;
        !            96: {
        !            97:        /* Returns the time of last access for the named device.
        !            98:         * The name given as taken as the last component of the device
        !            99:         * pathname.  The first component, "/dev/" is supplied by this
        !           100:         * routine.  If the device doesn't exist, -1L is returned.
        !           101:         */
        !           102: 
        !           103:        char dev[20];
        !           104:        struct stat statb;
        !           105: 
        !           106:        strcpy(dev,"/dev/");
        !           107:        strcat(dev,s);
        !           108:        if( stat(dev,&statb)<0 )
        !           109:                return(-1L);
        !           110:        return( statb.st_atime );
        !           111: }

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